[Samwise]

"Both Elves and Men are the Children of Ilúvatar, and so have much in common, but there are also great differences between the two peoples. Of these, the most significant is that Elves are 'immortal', at least while the World lasts; they do not suffer ageing or disease, and if they are slain or wither with grief, they are reincarnated in the Halls of Mandos in Valinor.
Although, unlike Men, the Elves must remain in the world until its ending, they are not bound to Middle-earth. They may if they wish take the straight road, and sail into the Uttermost West, a road that is barred to mortals.

[Maigret]

Thanks for the explanation, Samwise :)